The present invention relates to an electron beam exposure apparatus which is used in a manufacturing process of a semiconductor device and an exposing method using an electron beam, and especially relates to an electron beam axis adjustment of a variable shaping type electron beam exposure apparatus.
An electron beam exposure apparatus is used as a lithography apparatus for forming a circuitry pattern of an original mask, used in an exposure process of the semiconductor device or fordirectly forming a circuitry pattern on a silicon wafer substrate.
In the exposing method of the electron beam exposure apparatus, there are a raster-scan system for shaping a pattern by scanning a surface of the sample while the electronic source is reduced and the electron beam is switched on and off, a variable shaping system for generating a variable rectangular beam, by shaping, with plural rectangular apertures, the electron beam generated from a electronic source and by scanning this shaped rectangular aperture image with a deflector, and a partial batch exposure system to repeatedly shape figures on a transfer mask beforehand and to irradiate the electron beam so as to expose with a high reduction rate, as an improved one of more variable formation system. Especially as compared with a raster-scan system, since the variable shaping system exposes a whole figure, having a big area, the number of shots can be significantly reduced, and speedup becomes possible. However, since in a variable shaping system, a complicated electron optics system apparatus, such as a beam shaping deflection system, is necessary, there is a problem that a beam axis difference occurs in the variable shaping deflection.
FIG. 1 is a perspective view showing a brief construction of the electron beam exposure apparatus, and FIG. 2 is a partial enlarged view of FIG. 1 to show a locus of the electron beam. The electron beam exposure apparatus shown by FIG. 1 is operated with a variable shaping system, and in FIG. 2, a focal (or image) location of an electron source is shown with a circle (it appears as an ellipse because it is show in the perspective view), and an image location of the shaping aperture is shown by arrows. In other words, the electronic source 1 and an electronic source image 24 are shown by a circle and a shaping aperture image 25 is shown by the arrows.
Generally, the shaping aperture is reduced about one to a dozen times with a reducing lens, and the electron source image is magnified a corresponding number of times. The first shaping aperture image is focused on the second shaping aperture with a shaping lens, a shaping deflector moves the first shaping aperture image, and controls a beam shape transmitting the second shaping aperture. Here, an electronic source image is focused on the center of the shaping deflector, and an imperfect axis alignment of the electron source image occurring due to a lower lens should be prevented in the operation of the shaping deflector. In other words, if the condition of the shaping lens, the location of the aperture, the beam axis etc. include an error, an imperfect axis alignment of the lower lens occurs, and there arises a bad influence in resolution or shot location precision when the shaping deflector is operated, that is, the dimension is varied.
As examples of an electron beam lithography device in which an imperfect axis alignment is adjusted by measuring a location difference of the electron beam, Japanese Patent Laid-open No. 6-236841 and Japanese Patent Laid-open No. 10-163089 are noted. However in these references, there is not any description of making the dispersion of the location difference a minimum by changing the focal point of the objective lens.
An objective of the present invention is to provide an electron beam exposure apparatus and a exposing method using an electron beam which realize [a] highly precise pattern lithography by preventing an imperfect axis alignment in the variable shaping operation.
In order to reach the above objective, in an electron beam exposure apparatus using a variable shaping system in an embodiment of the present invention, the imperfect axis alignment occurring when changing the beam dimension by varying an adjusting parameter of the lens or the shaping aperture, is measured to high accuracy so as to adjust the shaping lens, and a transcription distortion and location difference, appearing when the dimension changes, are prevented. Thereby, a beam adjusting method which is capable of achieving high resolution of the electron beam exposure apparatus of a variable shaping type can be offered.
That is, the electron beam exposure apparatus in accordance with an embodiment of the present invention comprises, an electron source for generating an electron beam, a first shaping aperture for shaping the electron beam, a shaping lens for projecting the electron beam that passes said first shaping aperture on a second shaping aperture, a shaping deflector for generating a shaped beam by deflecting the projection image from said first shaping aperture so as to shape a cross-section of the electron beam transmitting the second shaping aperture, a reducing lens for reducing said shaped beam generated with said shaping deflector, an objective lens for focusing said shaped beam image of the shaped beam reduced with said reducing lens on a sample surface, an objective deflector for deflecting said shaped beam to a desired location of said sample surface, a shaping axis adjusting deflector which is arranged on an upper shaping lens and controls an incidence angle of said electron beam to said shaping deflector, an objective axis adjusting deflector which is arranged between the second shaping aperture and the objective lens and controls said incidence angle of said shaped beam to said objective lens, a detector for detecting a reflected electron beam which is generated by scanning said sample surface with the shaped beam with said objective axis adjusting deflector, a deflector output value adjusting means for adjusting said various deflectors so as to obtain a minimum output value of deviation from said objective deflector, said shaping axis adjusting deflector and said objective axis adjusting deflector, by scanning said sample surface with plural different shaped beams using the second shaping aperture, and a shaping lens adjusting means for setting an adjusting parameter of the shaping lens so as to make dispersion of the location difference minimum by changing a focal point of said objective lens, by measuring a location on said sample surface of said shaped beam based on information from said detector, by measuring said location difference of said shaped beam before and after said changing, and by obtaining said dispersion of said location difference in said output value of respective ones of said deflectors corrected with said deflector output value adjusting means.
Furthermore, the electron beam exposure apparatus implemented as an embodiment of the present invention comprises, an electron source for generating an electron beam, an accelerating means for accelerating said electron beam, a first shaping aperture for shaping the electron beam, a shaping lens for projecting the electron beam that passed said first shaping aperture on a second shaping aperture, a shaping deflector for generating shaped beam by deflecting the projection image from said first shaping aperture so as to shape a cross-section of the electron beam transmitting the second shaping aperture, a reducing lens for reducing said shaped beam generated with said shaping deflector, an objective lens for focusing said shaped beam image of the shaped beam reduced with said reducing lens on a sample surface, an objective deflector for deflecting said shaped beam to a desired location of said sample surface, a shaping axis adjusting deflector which is arranged on an upper shaping lens and controls an incidence angle of said electron beam to said shaping deflector, an objective axis adjusting deflector which is arranged between the second shaping aperture and the objective lens and controls said incidence angle of said shaped beam to said objective lens, a detector for detecting a reflected electron beam which is generated by scanning said sample surface with the shaped beam with said objective axis adjusting deflector, a deflector output value adjusting means for adjusting said various deflectors so as to obtain a minimum output value of deviation from said objective deflector, said shaping axis adjusting deflector and said objective axis adjusting deflector, by scanning said sample surf ace with plural different shaped beams using the second shaping aperture, and a shaping lens adjusting means for setting an adjusting parameter of the shaping lens so as to make dispersion of the location difference minimum by changing a voltage applied to said accelerating means for accelerating said electron beam, by measuring a location on said sample surface of said shaped beam based on information from said detector, by measuring said location difference of said shaped beam before and after said changing, and by obtaining said dispersion of said location difference in said output value of respective said deflectors corrected with said deflector output value adjusting means.
Furthermore, the electron beam exposure apparatus implemented as an embodiment of the present invention comprises, a beam shaping means for generating an electron beam having an arbitrary cross-section by projecting said electron beam to several shaping apertures, a first detector for detecting a first reflected electron beam which is generated by scanning a reference mark on a sample with a shaped beam generated by said beam shaping means, a focal location shift means for shifting a shaft of said shaped beam from a focal location of a lens on a reference location of said shaped beam which is determined based on a first location information of said shaped beam provided with said first detector, a second detector for detecting a second reflected electron beam which is generated by scanning said reference mark on said sample with said shaped beam which is shifted an axis thereof with said focal location shift gateway, and a lens adjusting means for adjusting said lens, wherein a location difference of said shaped beam is measured based on a second location information of said shaped beam provided with said second detector, and an adjusting parameter for said lens is obtained in which dispersion of said location difference becomes minimum.
Furthermore, the electron beam exposure apparatus implemented as [the other] another embodiment of the present invention comprises [comprising], a lens adjusting means for changing said adjusting parameter of said lens based on a value of said location difference of the electron beam on said sample by changing said adjusting parameter of said lens.